The present disclosure relates to reflective optical systems and in particular relates to three-mirror anastigmatic optical systems or telescopes. Such systems may be utilized in any number of settings, including but not limited to ground to space based observation, space to space based observation, and space to ground based observation, for any number of purposes, including but not limited to astronomical research, commercial terrestrial imaging, and reconnaissance.
Conventional three mirror anastigmatic optical systems generally comprise at least three non-flat optical elements: a primary mirror, a secondary mirror, and a tertiary mirror. The combination of the three mirrors in such systems is configured to correct for spherical aberration, coma, and astigmatism. An example of a conventional all-reflective focal three-mirror anastigmat telescope is illustrated by U.S. Pat. No. 4,101,195 to Korsch, entitled “Anastigmatic Three-Mirror Telescope,” the entire contents of which are incorporated herein by reference. Korsch discloses a focal three-mirror telescope having ellipsoidal primary and tertiary mirrors, and a hyperbolic secondary mirror, with the three mirrors producing an image in a conveniently located finite plane for viewing, or measurement.
Some optical systems require multiple light paths, or channels, to provide for different measurement phenomenology. Such channels may be defined by, for example, light beams of particular wavelength bands (i.e. visible channels or infrared channels). To enhance performance in each channel, optical designs often use common fore-optics assemblies, (i.e. comprising the primary and secondary mirrors), and different tertiary and/or quaternary mirrors, each having different prescriptions for each channel.
Manufacturing tertiary mirrors and/or quaternary to different optical prescriptions may add to the cost of an optical system, for example by increasing the time and resources needed to fabricate the tertiary or quaternary mirrors to the different optical prescriptions, and by decreasing the number of similar elements in the optical system. Additionally, the use of differently shaped tertiary (or quaternary mirrors) may result in an additional testing and integration costs.
Furthermore, in some optical systems, utilizing different tertiary (or quaternary) mirrors when collecting and separating different channels of electromagnetic radiation may result in awkward asymmetrical packaging for the telescope system elements, as well as the totality of the optical system. Such packaging may further increase the cost of manufacture, with added expense to fabricate a broadly asymmetrical mount, as well as increased integration costs.
What is needed is a simplified way to economically manufacture three mirror anastigmatic optical systems.